1. Field of the Invention
The present invention relates to wick-based liquid emanation systems, and more particularly to (i) a wick-based liquid emanation system having a child-resistant overcap, and (ii) a child-resistant overcap for use with the wick-based liquid emanation system.
2. Description of the Related Art
Wick-based liquid emanation systems are known in the art for dispersing into the air vaporized particles of any number of liquids. Such systems are often used in the home with liquids varying from insect repellent to air freshener. Typically, in such systems, one end of a wick is partially submerged in the liquid to be dispersed. The liquid is contained in any suitable container. The partially submerged portion of the wick absorbs the liquid, some of which diffuses by capillary or wicking action into the exposed, unsubmerged portion of the wick. The exposed portion of the wick is locally heated, often by means of a ring-shaped heater which fits over the wick. This causes the liquid which has diffused into the exposed portion of the wick to molecularize or evaporate into the surrounding air. Continual application of heat to the exposed portion of the wick results in an evaporation/absorption process that continues until the liquid is consumed.
A problem with conventional wick-based liquid emanation systems, as with many products suitable for home use, is the potential that a child will come into contact with the liquid contents of the system. For example, this can occur when the child tampers with the system or if the system is accidentally tipped over, the contents spilled and left for the child to discover. Many of the liquids utilized with such systems can be harmful if ingested, and some are harmful if merely contacted. Therefore, it is desirable to make these systems "child-resistant" and "spill-resistant" to reduce the chance that a child will access the potentially harmful contents of the system.
An additional concern is the potential that the contents of the system will be prematurely lost through spillage or evaporation. Therefore, it is desirable to provide a sealed system in which the contents are retained inside prior to use.
In addition, it is desirable that the system provide some indication as to whether it has been opened, alerting users to the potential that some of the contents may have been spilled or otherwise depleted.
One possible approach is to provide a dispenser cap that protects the contents of the system prior to use or that regulates access to the contents during use, or both. Many attempts have been made to develop child-resistant or tamper-evident dispenser caps for use with various products.
U.S. Pat. No. 5,121,859 ("the '859 patent") to G. Stull, entitled "Non-resealable Dispenser Cap Construction", shows a non-resealable dispenser cap for use with hand-held dispensers. The cap has an elongated tapered, stepped hollow spout with a discharge orifice. A closure cap having a transverse closure wall is mounted on the spout. The transverse wall engages and closes over the discharge orifice. With the closure cap so mounted, the transverse closure wall is distorted and biased by its engagement with the wall of the discharge orifice. Either the closure cap or the spout is formed with two oppositely-disposed frangible tabs which overlie and are permanently attached to the other. Each tab has a zone of weakness that can be readily ruptured by rotating either the cap or the spout.
U.S. Pat. No. 2,930,063 ("the '063 patent") to M. Stull, entitled "Dispensing Cap for Containers", shows a flexible plastic applicator cap for use with small hand-held containers. The cap has a body adapted to be attached to the container. A hollow, cylindrical spout is integral with and extends an appreciable distance from the body. The tip of the spout has a transversely disposed, annular, external end face making an acute angle with the spout's axis, having a discharge orifice surrounded by the surface of the end face and having a stopper formed with walls of reduced thickness at its base. The walls are integral with the spout and project from the end face thereof. The cap may be readily cut or torn. Thereby, the stopper (at the reduced walls thereof) is severed from the spout to reveal the discharge orifice. The stopper has an extremity of reduced diameter for closing the orifice.
U.S. Pat. No. 3,083,858 ("the '858 patent") to Biedenstein, entitled "Tear Type Container Closure", shows a container closure which is integrally connected to the container by a frangible connection. The closure may be separated from the container by a pull on the closure. This tears the frangible connection, but leaves a major portion of the material of the frangible connection attached either to the closure or the container where it will be active as a temporary resealing means between the closure and the container.
U.S. Pat. No. 4,757,911 ("the '911 patent") to Larkin et al., entitled "Container and Closure Construction", shows a thin flexible fluid-tight cover of PVC bonded to a rigid port of a diluent container for use in medicinal applications and which is to be subjected to heat sterilization. The cover includes an outer flange for bonding to a complementary surface around the port, and a removable section for spanning the port. The removable section includes a central flexible diaphragm and a cylindrical wall. The diaphragm is axially expandable by flexing of an annular convolution. A frangible tear line joins the cylindrical wall to the outer flange. The cylindrical wall is disposed adjacent the outer surfaces of an abutment wall on the port to provide stress relief against rupture of the tear line from stresses generated in the cover during sterilization. A pull ring attached to a narrow post is located adjacent the wall for concentrating manual pulling forces to a limited segment of the tear line.
U.S. Pat. No. 5,249,695 ("the '695 patent") to Luch et al., entitled "Spout Fitment Closure Plug", shows a spout fitment adapted to be attached to and surround a hole in a container, particularly a paperboard carton or other flexible container. The spout fitment has internal threads and an external flange which seals around the hole and is fixed to the container by thermal means, adhesive or the like. A cap has a top disk from which an externally threaded skirt depends. The lower edge of the skirt seals against a sealing membrane on the spout. Surrounding the skirt is a tamper-evident band attached to the lower edges of gripping ribs by frangible bridges. The tamper-evident band has a locking device engaging a complementary locking device on the fitment. Thus, the cap cannot be unscrewed without removing the tamper-evident band.
U.S. Pat. No. 5,201,440 ("the '440 patent") to Gross, entitled "Closure with Tamper-evident Tear-off Panel with a Flow Control Element", shows a container closure which includes a body for mounting on the container. The body defines a dispensing orifice. A flow control device, such as a lid, is disposed on the body and moved between positions opening and closing the dispensing orifice. A tamper-indicating member is connected by a first frangible web to the lid. An anchor is connected with a second frangible web to another portion of the tamper-indicating member, and the anchor is retained by the closure body. The tamper-indicating member also includes a graspable pull tab, which can be pulled to completely sever the frangible webs, permitting the lid to be opened while providing evidence of tampering with the closure.
A problem with these cap configurations, however, is that they are not particularly suited for use with a liquid emanation system which employs a wick. Nor do they provide "child-resistant" or "spill-resistant" closures for such wick-based liquid emanation systems.
Additionally, the foregoing configurations do not address a further problem which is often encountered with such wick-based liquid emanation systems, namely, the condensation that can accumulate on the heating mechanism and other parts of the system due to excess emanation. If the wick extends a considerable length above the liquid, emanation will occur over the entire length, often leading to condensation of excess moisture on the heating device and the remainder of the system, which is inconvenient and can be potentially damaging. One possible solution to this problem would be to limit the length by which the wick extends from the liquid. However, if the wick only extends slightly above the surface of the liquid, then it becomes very difficult to heat the wick without heating the liquid reservoir as well. This can lead to additional problems such as direct evaporation of the liquid.
Accordingly, there is a need for a wick-based liquid emanation system, and for a closure for use with a wick-based liquid emanation system, which overcome these and other drawbacks.
There is also a need to provide a closure for use with a wick-based liquid emanation system that is particularly suited to resist tampering or access by children. (Hereinafter, a wick-based liquid emanation system and closure therefor will collectively be referred to as a "system.")
There is a further need for such a system which indicates whether the system has been opened.
There is yet another need in the art for such a system which controls the rate of liquid emanation from the system.
There is an additional need in the art for such a system which can be inexpensively manufactured.